Influence of different levels of Drip Irrigation and Mulching on Quality Parameters and Major Nutrient contents in Mulberry

Influence of different levels of Drip Irrigation and Mulching on Quality Parameters and Major Nutrient contents in Mulberry

Ranjitha. H. O^* , S. Chandrashekhar

Department of Sericulture, University of Agricultural Sciences, Gandhi Krishi Vignan Kendra, Bengaluru – 560065, Karnataka – India

Corresponding Author Email: agrico.r.dd@gmail.com

DOI : http://dx.doi.org/10.53709/CHE.2021.v02i01.005

Abstract

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INTRODUCTION

Karnataka stands first in mulberry sericulture for many decades but now a day’s sericulture farmers withdrawing silkworm rearing due to insufficient and irregular rainfall, which minimizes the recharging of groundwater table causing acute shortage of water for drip, as well as irrigation for mulberry garden, results in shrinkage of mulberry acreage. Added to this, almost all the mulberry growing framers irrigate the crop field without knowing crop water requirement, which leads to unnecessary wastage of water during dry spells. , The higher moisture content of mulberry leaf, is one of the essential criteria which has a direct effect on the growth and development of silkworms.In order to increase water productivity, the new system of irrigation and new methods of water conservation techniques are needed to be implemented. Moisture content in mulberry leaves improves ingestion and digestion also helps in the conversion of nutrients in the silkworm body. Moisture content in mulberry leaves is considered one of the most important criteria in assessing the leaf quality [1-2] stated that drip irrigation is most important in enhancing the availability and absorption of significant nutrients like nitrogen and other essential minerals in the plant, thereby collectively increase the chlorophyll content of the leaves. Mulberry leaf production and productivity depend on soil moisture and nutrients availability, and it is observed that drip irrigation surges the leaf yield of mulberry plants by 68 percent [3]. Hence, higher leaf production and productivity are achieved by improved methods of irrigation along with moisture conservation measures like mulching.

Material and Methods

            The experiment was conducted during winter 2019 at the Department of Sericulture, University of Agricultural Sciences, Gandhi Krishi Vigyan Kendra, Bangalore. The field is located at a latitude of 12°58′ N, the longitude of 77°35′ east and an altitude of 930 m above mean sea level in the Eastern Dry Zone (Zone-5) of Karnataka. V-1 mulberry variety was chosen for the experiment, and the garden was middle pruned and ploughed followed by clod crushing and harrowing. FYM was applied at the 20 t ha^-1 year^-1 and incorporated into the soil homogeneously by hoeing. The gardens were maintained with the recommended package of practices [4] uniformly during the experimentation. The experiment was laid out in a strip plot design consisting of eight treatment combinations and replicated five times.

Treatment details

The experiment was laid out in a strip plot design consisting of two factors in the investigation viz., Factor A – levels of irrigation (L₁-0.5 CPE, L₂-0.6 CPE, L₃-0.7 CPE, and L₄-0.8 CPE) and Factor B – levels of mulching (M₁-with mulching and M₀-without mulching), The combination of both factors, comprises eight treatment combinations and is replicated five times.

Mulching

Mulching to the plot was done by covering the soil surface uniformly on both sides of mulberry plants paired rows with a 70-micron thick UV stabilized black polythene mulch film.

Drip irrigation

The chosen drip irrigation method was laid out in a mulberry garden with 16 mm in-line drip laterals, which were connected to sub mains and laid on the surface all along the paired rows and in-line drippers were placed on lateral tubes at a distance of 40 cm with the rate of discharge of 2.5 lph. One end of the lateral tube was connected to sub mains, and another end of the tubes was closed with end caps. Each lateral is fitted with a 16 mm tap for controlled irrigation as per the experimental plan. The lower end of the sub-main was connected with the flush valve.

The blank irrigation was given to the whole experimental plot two days before starting of an experiment to bring the moisture level of the soil to field capacity. Following irrigations were given three days once, and different irrigation treatments were executed on the basis of Cumulative Pan Evaporation (CPE) through a climatological approach [5]. The total quantity of water applied to individual plots at each irrigation was measured through the fixed water meter. The calculated volume of water was supplied to different treatment plots during each irrigation.

Collection of experimental data

 A sample comprising of five plants for each treatment was randomly selected and labelled for recording various observations. The observations on different quality parameters were recorded at 30, 45, and 60 DAP. Primary nutrient contents (NPK) were recorded at 60 DAP (at harvest). The methodology and procedure followed to record the observations are presented below:

Quality parameters

Leaf moisture content (%)

            Relative moisture content of the mulberry leaf was assessed through the gravimetric method by taking the difference between fresh weight and dry weight of leaves and stated as a percentage on a fresh weight basis (A.O.A.C., 1980).   

                              Fresh wt. – dry wt. 

Leaf moisture % = ————————×100                                                     

                                     Fresh weight

Protein content of the leaf (%)

Protein content of the leaf was assessed after determining the total nitrogen content in the leaf (0.5 g leaf sample) using Micro-Kjeldhal’s method. The protein content of the leaf was computed by multiplying the percent nitrogen of the sample with the factor 6.25 [6].

Carbohydrate content of the leaf (%)

Carbohydrate content in the leaves of mulberry was quantitatively measured by the Anthrone Reagent method [7]. For assessment of carbohydrates content, 0.2 g of mulberry leaf sample was grinded in pestle and mortar with the help of distilled water. The samples were centrifuged at 5000 rpm for 10 minutes. The supernatant was collected in test tube, and 4 ml of anthrone reagent is added to get the green color. The absorbance value of the green color was noted to evaluate the carbohydrate content using U-V spectrophotometer at a wavelength of 625 nm. Against standard sugar solution (Dextrose L) the carbohydrates content was calculated and expressed in mg/g.

Chlorophyll content of leaves

The chlorophyll content of mulberry leaves was recorded by using SPAD meter, and the average (SPAD-Soil Plant Analysis Development) chlorophyll content of top, middle, and bottom leaves was recorded randomly selected five plants and presented.

Major nutrient contents (NPK)

NPK analysis

Fresh leaf samples of mulberry were collected from each treatment at 60 DAP for biochemical analysis. The collected mulberry leaf samples at the time of harvest were subjected to drying in a hot air oven at 60° C for 2 hours. Later the samples were powdered by using a grinder fitted with stainless steel blades and well-preserved in polythene covers for further chemical analysis [8]. The leaf nitrogen, phosphorus, and potassium contents were estimated using the standard reference of the AOAC (1980) protocol. The nitrogen content of leaves was evaluated by adopting the Micro Kjeldhal digestion distillation method.

Digestion of plant samples by using di-acid mixture: A powdered dry mulberry leaf sample of 0.5 g was pre-digested by using 5 ml of concentrated HNO₃ and once again digested with a di-acid mixture (HNO₃: HClO₄ in the proportion of 10:4 ratio). The volume of the digested mixture was made up to 100 ml with the help of distilled water, and the mixture was preserved for further elemental analysis [9]. The total phosphorus content was determined by taking a known amount of digested mixture, and by adopting the Vanadomolybdophosphoric yellow color method, phosphorous content was estimated as described [10]. Using the respective di-acid, the total potassium content of the leaf samples was estimated by atomizing the digestion mixture to the calibrated flame photometer under suitable conditions [11].

Statistical analysis: Data recorded on mulberry were analyzed statistically by using Stat software WASP (strip plot). The treatment means and interaction effects were compared using critical difference values at 5 percent. The significance level used in F and t-tests was P=0.05 for strip plots [12]. The critical difference (CD) values were computed where the F-test was found significant.

Results and Discussion

In the present study, results revealed that mulberry responded differently to different levels of irrigation, mulching, and their interaction effect in terms of growth, yield, and quality parameters of the mulberry leaf has been investigated, as research was done in strip plot where interaction effect results are calculated. The quality parameters are presented in table 1.

Relative moisture content: At 30 DAP, therelative water content of mulberry leaves(%) differed significantly due to different levels of mulching and irrigation. The highest relative water content (79.68%) was recorded in mulching, and the lowest (78.28%) was recorded without mulching. Among different levels of irrigation higher level of irrigation 0.8 CPE showed the maximum relative water content (81.21%), which was found on par with (80.14 %) 0.7 CPE, and minimum (76.57%) was recorded in 0.5 CPE. At 45 DAP,therelative water content of mulberry leaves(%) differed significantly due to different levels of mulching and irrigation. The highest relative water content (71.92%) was recorded in mulching, and the lowest (71.17%) was recorded without mulching. Among different levels of irrigation higher level of irrigation 0.8 CPE, showed the maximum relative water content (72.73 %), and minimum (70.34 %) was recorded in 0.5 CPE.

At 60 DAP,therelative water content of mulberry leaves(%) differed significantly due to different levels of mulching and irrigation. The highest relative water content (65.60 %) was recorded in mulching, and the lowest (64.80 %) was recorded without mulching. Among different levels of irrigation higher level of irrigation 0.8 CPE, showed the maximum relative water content (66.80 %) whereas minimum (63.84 %) was recorded in 0.5 CPE. Bongale and siddalingaswamy (2003) came up with the same results that at a higher level of irrigation (0.9 CPE) during the non-rainy period noticed higher leaf moister content under drip irrigation. [13] studies are in line with the present investigation that maximum coarse leaf moisture content (60.09 %) was noticed in single row drip irrigation.

Chlorophyll content: At 30 DAP, the chlorophyll content of mulberry leaves (SPAD meter readings) differed significantly due to different levels of mulching and irrigation. The highest chlorophyll content (8.19) was recorded in mulching, and the lowest (7.86) was recorded without mulching. Among different levels of irrigation higher level of irrigation 0.8 CPE, showed the maximum chlorophyll content (8.48), whereas a minimum (7.64) was recorded in 0.5 CPE. At 45 DAP, the chlorophyll content of mulberry leaves (SPAD meter readings) differed significantly due to different levels of mulching and irrigation. The highest chlorophyll content (8.51) was recorded in mulching, and the lowest (8.19) was recorded without mulching. Among different levels of irrigation higher level of irrigation 0.8 CPE, showed the maximum chlorophyll content (8.84), whereas a minimum (7.83) was recorded in 0.5 CPE. At 60 DAP, thechlorophyll content of mulberry leaves (SPAD meter readings) differed significantly due to different levels of mulching and irrigation. The highest chlorophyll content (6.80) was recorded in mulching, and the lowest (6.43) was recorded without mulching. Among different levels of irrigation higher level of irrigation 0.8 CPE showed the maximum chlorophyll content (7.44), whereas the lowest (6.01) was recorded in 0.5 CPE. The results conform with the earlier studies of [14], who reported an increase in chlorophyll content with an increase of irrigation water application parallelly enhanced soil moisture. This is also supported by the study of [15], where leaf quality of five varieties namely DD, V-1, S-54, M-5, and S-36 were evaluated for leaf moisture content; among all the varieties, V-1 recorded the highest chlorophyll content of the leaf.

Protein content: At 60 DAP, the protein content of mulberry leaves (%) differed significantly due to different levels of mulching and irrigation. The highest protein content (12.63 %) was noted in mulching and the lowest (11.35 %) was recorded without mulching. Among different levels of irrigation higher level of irrigation 0.8 CPE, showed the maximum protein content (14.39 %), whereas minimum (9.10 %) was recorded in 0.5 CPE.

Carbohydrate content: Carbohydrate content of mulberry leaves (%) differed significantly due to different levels of mulching and irrigation. The highest carbohydrate content (15.86 %) was recorded in mulching, and the lowest (15.14 %) was recorded without mulching. Among different levels of irrigation higher level of irrigation, 0.8 CPE, showed the full carbohydrate content (16.59 %), whereas minimum (14.48 %) was recorded in 0.5 CPE. These results are following the findings of [16], who reported the maximum protein content of coarse leaves to be 15.57 percent under 0.8 CPE with drip irrigation. Similar findings are reported by [17] where total protein and total carbohydrate content showed the statistically non-significant difference when irrigated with the same quantity of water and showed significant difference with the variation of irrigated water in the V-1 mulberry garden.                 

Discussion: On the basis of the present study, it can be inferred that quality parameters are greatly influenced by available moisture content in the root zone [18]. Mulberry being a deep-rooted perennial crop surface drip method will not only save the irrigation water, but also reduce the frequency of irrigation and seepage accompanied with plant nutrients and are effective because of their close association with rhizosphere zones of mulberry and making use of water efficiently [19].
An increase in soil temperature and moisture content promotes nutrient uptake as well as stimulates root growth; therefore, mulched plants usually grow and mature more uniformly than unmulched plants [20]. Uniform root growth along with sufficient water in the root zone stimulates the plant to uptake more water which contributes to the moisture content of the leaf in higher levels of irrigation.

Chlorophyll is a natural pigment found in green plants, and its content is an essential variable in assessing the plant’s physiological state and photosynthetic performance, the basic process for vegetation life. The total chlorophyll content is significantly higher in tender leaves and maximum in medium matured leaves. However, the exceptionally minimum content of total chlorophyll was observed in coarse leaves but in the present investigation, due to mulching and higher levels of irrigation, chlorophyll content was found little higher in 60 DAP than 30 DAP highest in 45 DAP as recorded in similar findings. Higher chlorophyll content indicates the photosynthetic efficiency; thus, it is can be used as one of the criteria for quantifying photosynthetic rate in mulberry [21]. The enhanced carbohydrate status also may be attributed to higher photosynthetic efficiency due to the presence of higher chlorophyll levels [22].

The maximum protein content in the leaves was found to be in higher levels of irrigation (0.8 CPE) in the present study and decreases as it goes with the lower irrigation levels (0.5 CPE) similar trend is followed in terms of mulching. This might be because protein-synthesizing mechanism is greatly affected by water stress conditions where the activity of protease enzyme is in increased condition or may be due to proteolysis.

Carbohydrates are of particular importance in plant metabolites since they are direct products of photosynthesis, and the primary energy storage components and a variety of other organic compounds are synthesized from carbohydrates. Carbohydrates, which influence quality and quantity of leaf yield. In mulberry leaves, carbohydrates are available in plenty, and it was reported to be the chief source of energy for silkworms [23]. In the present investigation, total carbohydrate content is an increasing level as the irrigation level increases it might be due to the reason that absorption of mineral content is more in higher moisture level, which adds to the synthesis of more sugars in the mulberry leaves [24].

The results of interaction effects of quality parameters are presented in table 1b where,theinteraction effect of irrigation levels and mulching showed a non-significant difference for relative water content, protein, and carbohydrate content. Chlorophyll content showed asignificant difference (at 60DAP) where lowest chlorophyll content (5.74) was recorded in T₅ (M₀ L₁) and found on par (6.078) with T₆ (M₀ L₂) and T₇ (M₀ L₃) (6.402). The combination (T₄) of 0.8 CPE and mulching showed higher values for all the parameters compared to lower levels of irrigation and without mulching.

Primary nutrient contents: The NPK contents are presented in table 2. Nitrogen content in mulberry leaf(%) differed significantly due to different levels of mulching and levels of irrigation. The highest nitrogen content (2.02 %) was recorded in mulching, and the lowest (1.82 %) was recorded without mulching. Among different irrigation levels higher level of irrigation,0.8 CPE, showed the maximum nitrogen content (2.32 %), whereas the lowest (1.48 %) was recorded in 0.5 CPE. Interaction effect of irrigation levels and mulching showed significant difference for nitrogen content of leaf. , The phosphorous content in mulberry leaf (%), differed significantly due to different levels of mulching and irrigation. The highest phosphorous content (0.48 %) was recorded in mulching, and the lowest (0.39 %) was recorded without mulching. Among different levels of irrigation higher level of irrigation, 0.8 CPE, showed the maximum phosphorous content (0.57 %), and minimum (0.26 %) was recorded in 0.5 CPE. The interaction effect of irrigation levels and mulching showed non – a significant difference in the phosphorous content of the leaf. Potassium content in mulberry leaf(%) differed significantly due to different levels of irrigation and differednon-significantly due to varying levels of mulching. The highest potassium content (1.51 %) was recorded in mulching, and the lowest (1.34 %) was recorded in without mulching. Among different levels of irrigation, a higher level of irrigation 0.8, CPE showed the maximum potassium content (1.51 %), whereas minimum (1.35 %) was recorded in 0.5 CPE. Interaction effect of irrigation levels and mulching potassium content of the leaf.

The current study is supported by [25] who reported nutrient use efficiency showed non – a significant difference for is 90 percent in the case of a drip irrigation system compared to furrow irrigation where it recorded only 40 percent. Higher nutritive and leaf yield was recorded in K-2 mulberry variety at 70 CPE in 2 feet by 2 feet garden. Similar findings were recorded by [26]

who reported drip irrigation was found effective in increasing availability and absorption of nitrogen and other minerals in mulberry leaf. In support to the present investigation, [27] reported that phosphorous and potassium found significant in higher levels of irrigation and mulching. , The nutritional composition of mulberry leaves, will influence the economical parameters of the cocoon, which depends on leaf moister level, protein, carbohydrate, and mineral content which plays an essential role during the development of the early stages of silkworm [28]. So, an increase of quality linked to mulberry leaf productivity per unit area is very important, achieved by drip irrigation.

Conclusion

Mulberry leaf is the major economic component in sericulture, where the production of quality leaf per unit area has a direct effect on cocoon quality. Moisture content mulberry leaves is considered one of the most important criteria in assessing the leaf quality (Paul et al., 1992). In levels of irrigation 0.8 CPE found most effective with black plastic polythene mulch compared to the conventional method of irrigation in utilizing the scarce resource like water and along with that plastic mulching helps to save the water in the root zone which helps the plant to maintain sufficient moisture level to uptake the available nutrients in the soil.

Table 1a: Quality parameters of mulberry leaf influenced by different levels of drip irrigation (I) and mulching (M)

*Significant at 5%, NS- Non significant, DAP – Days after pruning

CPE – Cumulative pan evaporation,

Mulching levels – (M)                         Irrigation levels – (I)

M₁ = with mulching                              L₁ = 0.5 CPE

 M₀ = without mulching                        L₂ = 0.6 CPE

                                                              L₃ = 0.7 CPE

                                                              L₄ = 0.8 CPE
Table 1b: Quality parameters of mulberry leaf influenced by interaction of different levels of drip irrigation and mulching

*Significant at 5%, NS- Non significant, DAP – Days after pruning

CPE – Cumulative pan evaporation

Mulching levels – (M)                         Irrigation levels – (I)

M₁ = with mulching                              L₁ = 0.5 CPE

M₀ = without mulching                         L₂ = 0.6 CPE

                                                              L₃ = 0.7 CPE

L₄=0.8CPE

Table 2: Major nutrient contents of mulberry leaf influenced by different levels of drip irrigation and mulching

*Significant at 5%, NS- Non significant, DAP – Days after pruning

CPE – Cumulative pan evaporation

Mulching levels – (M)                         Irrigation levels – (I)

M₁ = with mulching                              L₁ = 0.5 CPE

 M₀ = without mulching                        L₂ = 0.6 CPE

                                                              L₃ = 0.7 CPE

                                                              L₄=0.8CPE

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